1. Field of the Invention
This invention relates to a method of equalizing synchronous digital data when such synchronous digital data are transmitted through lines of an arbitrary length and also to a synchronous data interface circuit to which the equalizing method is applied.
2. Description of Related Art
When a non-return to zero (NRZ) data signal is transmitted through a line of an arbitrary length, deterioration of the transmission characteristics, particularly of the amplitude distortion characteristic, of the line will cause distortion of the signal waveform, resulting in deterioration of the eye pattern at the signal receiving end of the line. Therefore, in order to minimize the deterioration represented by the eye pattern, conventional synchronous data interface circuits first pass a received NRZ data signal through an equalizer to compensate for amplitude distortion of the NRZ data signal, and then reproduce its original signal by a discriminator. Further, in order to receive a plurality of NRZ data signals, equalizers are provided for individual signal paths, and they perform compensating processing for amplitude distortion independently of each other.
In these conventional synchronous data interface circuits, since the equalizers operate independently of each other to compensate for amplitude distortion of data signals, each equalizing circuit is large in scale, and particularly when a plurality of NRZ data signal paths are provided, total volume of interface circuit becomes great in size and the power consumption is also high.